One of the many strengths of the TV adaptation of 'Zen' (Sunday, BBC One) is that it caught the gloom of Italy as well as the glamour. While it’s been shot on the streets of Florence, they have been bathed in a faintly sinister lemonish light – the visual equivalent of acid reflux. At the same time everything has been pleasingly layered with conflicting forces – especially Rufus Sewell’s Zen.

Sewell may not look like the sort of man who’s greatly troubled by insecurities, particularly where women are concerned, but he was excellent at conveying someone whose outward flashiness – sharp suits and sunglasses – is balanced by a far-from-flashy private life. Not only does he live with his mum, but he agonises about asking Tania (Caterina Murino), the office beauty, on a date. Nor does Zen take any pride in his reputation for ‘scrupulous integrity’. Rather, it’s like an unfortunate birthmark that prompts sniggers of derision from his unapologetically venal colleagues.

Although there’s nothing new about having British actors playing non-British people, but chattering happily away in English – see K Branagh/Wallander – I’ve never seen it done this well before – largely, I think, because 'Zen' had carved out such a distinctive visual identity. It even had Sewell watching Italian TV without it seeming unduly odd.

Scriptwriter Simon Burke had managed to keep the complexity of Dibdin’s plotlines without sacrificing comprehensibility, while director John Alexander’s direction wasn’t just bold visually; it also took some big structural liberties. There’s an unwritten rule in British TV drama that no action sequence should last longer than five minutes – presumably in case anyone nods off, gets peckish or needs a wee. But here 'Zen' had a terrific scene in which the detective was trapped in a flooded cave which went on for ages, but never flagged for a moment.

At the end, Zen finally got to snog Tania in a lift. It says a good deal for his allure that, while choking with envy, I in no way begrudged him his moment of triumph.